Elevated Half Square
KQ6RH
(C) 1998, 1999, 2000
Ray Jurgens
(Up-Dated 2/25/2000)
Elevated Half Square
The elevated half square antenna is a very simple antenna that can be constructed from common materials yet gives significant improvement over a dipole at the same elevation. Ground mounted versions of this antenna are commonly used in amateur radio for 75/80 and 160 meter bands. The elevated version described here provides even greater performance. The Half Square antenna is bi-directional, has a low angles of radiation, is self supporting, is easily erected, and can be rotated with a TV antenna rotator. The Elevated Half Square antenna achieves its high level of performance by not radiating power at high angles of elevation where is leaks through the ionosphere and by having its high current regions near the top of the antenna. Figures 1 and 2 show the radiation patterns in azimuth and elevation.
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Figure 1 |
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Azimuth Pattern at 10 Degrees Elevation |
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Figure 2 |
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Elevation Pattern for the Elevated Half Square Antenna at 0 Degrees Azimuth |
This is one of the best DX antennas you can find unless you just happen to be able to put a 3 element Yagi at 90 to 120 feet in the air. Note that high angle radiation (local QRM) is attenuated by as much as 10 dB, so if you are in the central US, coastal stations will be attenuated, and the Europeans and western Pacific regions will be given 3.54 dBi gain. Forget about using this antenna for local work.
The pictures below show two ways to construct this antenna. There is the neat and light version made with fiberglass structures and the cheap, heavy and ugly PVC version. So take your pick.
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Figure 3 |
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Fiberglass Version of the Elevated Half Square Showing Structure and Feed |
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Figure 4 |
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PVC Version of the Elevated Half Square Showing the Structure |
There are a number of tricks to the design of the Elevated Half Square, and our Guide to the Elevated Half Square gives the complete details of the corrections for propagation velocity in dielectric tubes, methods of decoupling the feed line from the radiating structure, the construction of light weight structures to support the antenna and a complete parts list for both fiberglass and PVC structures. These topics are too extensive to cover on a web site, so this guide is listed in our Products Page.